Process for eliminating waste liquors accumulated in the desulfurization of coke oven gas

ABSTRACT

A process for eliminating waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier includes evaporating between 30 and 70% of the water from the waste liquor to provide a concentrated waste liquor solution. The concentrated waste liquor is introduced into a combustion chamber with air and coke oven gas. The concentrated waste liquor is thermally decomposed in the combustion chamber and eliminated sulfur is separated from the gaseous products of combustion. The gaseous products of combustion are admixed with the coke oven gas evolved during the coking process.

United States Patent [19] Diemer et al.

[ Dec. 2, 1975 l l PROCESS FOR ELIMINATING WASTE LIQUORS ACCUMULATED IN THE DESULFURIZATION OF COKE OVEN GAS [75] Inventors: Peter Dierner; Gerhard Preusser;

Paul Radusch, all of Essen, Germany [73] Assignee: Heinrich Koppers Gesellschatt mit beschrankter "aftung, Essen, Germany 22 Filed; Oct.31, 1974 21 Appl.No.:519,563

[30] Foreign Application Priority Data Dec. l3, 1973 Germany 236l9l0 [52] US. Cl. 423/567; 423/574 [51] Int. Cl. C01B 17/02 [58] Field of Search 423/567, 573, 574; 55/73 [56] References Cited UNITED STATES PATENTS 3,798,308 3/1974 Tatterson 423/574 1840.653 lO/l974 Diemer ct al. 423/573 Primary Examiner-G. O. Peters Attorney, Agent. or FirmStanley J. Price. Jr.

[57] ABSTRACT A process for eliminating waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier includes evaporating between 30 and 70% of the water from the waste liquor to provide a concentrated waste liquor solution. The concentrated waste liquor is introduced into a combustion chamber with air and coke oven gas. The concentrated waste liquor is thermally decomposed in the combustion chamber and eliminated sulfur is separated from the gaseous products of combustion. The gaseous products of combustion are admixed with the coke oven gas evolved during the coking process.

5 Claims, 1 Drawing Figure Dec. 2, 1975 US. Patent 5 T sm PROCESS FOR ELIMINATING WASTE LIQUORS ACCUMULATED IN THE DESULFURIZATION OF COKE OVEN GAS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process of eliminating waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier, and more particularly to a process for decomposing the waste liquor in a combustion chamber.

2. Description of the Prior Art Washing processes utilizing alkaline or ammoniacal washing solutions containing organic oxygen carriers have proven to be excellent in desulfurizing coke oven gas, that is, primarily removing the hydrogen sulfide from the coke oven gas. Useful organic oxygen carriers are quinones or compounds of quinoid character, such as hydroquinone, naphthoquinone, anthraquinone and their sulfonic acids. Other organic compounds with a suitable redox potential are also suitable. The process includes first washing the hydrogen sulfide from the coke oven gas in a washer of suitable design by means of the washing solution containing the organic oxygen carrier. The spent washing solution is then regenerated with air in an oxidizer where the oxygen of the air oxidizes the hydrogen sulfide to sulfur and water by means of the oxygen carrier contained in the washing solution. The sulfur is then removed from the washing solution by flotation and the regenerated washing solution is recycled to the hydrogen sulfide washer. In addition to the hydrogen sulfide removed from the coke oven gas, hydrocyanic acid that is also contained in the coke oven gas is removed by the above described washing process. The hydrocyanic acid is converted with the elemental sulfur to thiocyanates in the oxidizer. Also secondary reactions occur in the oxidization of hydrogen sulfide to sulfur to form sulfates, thiosulfates and other sulfur compounds. The washing solution is recycled and after an extended period of time the washing solution is enriched with the above compounds.

To prevent this enrichment it is necessary at certain intervals of time to discard a small portion of the recycled washing solution and replace it with fresh washing solution. This discarded enriched washing solution cannot be discharged directly into sewers or streams as a waste liquor. The substances contained in the enriched waste liquor are very toxic and consume oxygen so that expensive and difficult processing is required before the enriched waste liquor can be discharged into the sewer system. There is need for the inexpensive process for treating the discarded enriched waste liquor and avoiding discharge of the waste liquor into a sewer.

SUMMARY OF THE INVENTION This invention is directed to a process for eliminating the enriched waste liquor and avoiding discharging waste liquor into the sewer. The process includes first evaporating from the enriched waste liquor between 30 and 70% of the water contained in the enriched waste liquor to provide a concentrated enriched waste liquor. The concentrated enriched waste liquor is introduced into a combustion chamber where it is thermally decomposed with the addition of air in a reducing atmosphere. The reducing atmosphere is produced in the combustion chamber by combustion of coke oven gas evolved during the coking process. The sulfur is separated from the lean gas during the thermal decomposition of the waste liquor and the subsequent cooling of the lean gas.

With the above process the discarded enriched waste liquor is thus decomposed in a reducing atmosphere in which the sulfur compounds contained in the enriched waste liquor are converted essentially to hydrogen sultide and sulfur dioxide. The lean gas formed during the thermal decomposition is cooled and the elemental sulfur is separated from the lean gas and discharged from the process. The lean gas, together with the ammonia vapors formed during the thermal decomposition of the waste liquor is added to the coke oven gas before the primary coolers so that the lean gas and ammonia vapors participate in the complete treatment of the coke oven gas. Since the ammonia vapors accumulated in the treatment of the coke oven gas are simultaneously decomposed, another advantage of the process is the elimination of additional ammonia combustion equipmment which otherwise would be required for the destruction of the ammonia contained in the coke oven gas.

BRIEF DESCRIPTION OF THE DRAWINGS The FIGURE is a flow diagram illustrating the process for thermally decomposing enriched waste liquor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, the waste liquor discarded from the desulfurization system is conveyed through conduit 1 into the thickener 2. The thickener 2 is preferably in the form of a column provided with plates or trays. The waste liquor is introduced into the top of the thickener and flows downwardly on the plates or trays. The waste liquor discharged from the sump of the thickener 2 is circulated by pump 3 through conduits 4 and 6 between thickener 2 and the heater 5. The heated waste liquor is allowed to expand by means of an expansion valve 7 before it reenters the thickener 2 so that a portion of the water in the waste liquor vaporizes. The ammonia vapors accumulated during the vaporization are discharged from the thickener 2 through conduit 8 adjacent the upper portion of the thickener 2.

As soon as the waste liquor circulating between thickener 2 and the heater 5 has vaporized between about 30 and of its original water content, the thickened waste liquor is injected continuously through conduits 9 and 9a into the combustion chamber 10. The combustion chamber 10 includes a burner 11 that has an air feed conduit 12 for the primary combustion air. A conduit 13 is provided for the ammonia vapors, and coke oven gas is supplied through conduit 14. The feed conduit 12 for the combustion air has branch conduits 12a and 12b through which additional amounts of secondary air are injected into the combustion chamber 10. The air flowing through conduits 12a and 12b can be the waste air that forms in the oxidizers during the regeneration of the spent Washing solution.

The reducing atmosphere in the combustion chamber 10 is produced by combining in burner 11 the coke oven gas as well as the ammonia vapors accumulated during the treatment of coke oven gas with a deficiency of air, i.e. with a deficiency of oxygen. The sensible heat of the gas produced in this manner is sufficient to thermally decompose the thickened waste liquor that is injected into the combustion chamber through the conduits 9 and 9a with the simultaneous addition of air through conduits 12a and 12b.

The resultant gas of combustion referred to as a lean gas is discharged from the combustion chamber through conduit 15 and is introduced into a waste heat boiler 16 for cooling. The waste heat boiler 16 is connected by means of conduits 17 with the steam cylinder 18 in which the heater 5 is positioned. The necessary feed water for the boiler 18 is introduced to the system through conduit 19. It is possible by this arrangement to utilize the sensible heat of the lean gas for thickening the waste liquor and for simultaneously producing steam. The saturated steam produced in steam cylinder 18 is withdrawn through conduit 23 for subsequent use.

The sulfur accumulated in the waste heat boiler 16 during the cooling of the lean gas is discharged through conduit 20. The sulfur is conveyed through a submerged pot 21 and conduit 22 to a sulfur pit of the desulfurization system (not illustrated). The cooled and desulfurized lean gas leaves the waste heat boiler 16 through conduit 24. Conduit 8 carrying the ammonia vapors accumulated in thickener 2 is connected to the conduit 24 and is admixed with the lean gas conveyed therethrough. The mixture of cooled lean gas and ammonia vapors is then added to coke oven gas evolved during the coking process before the coke oven gas is introduced into the primary coolers (not illustrated). The slurry formed in the waste heat boiler 16 is discharged through conduit 25.

The following is an example of the above process utilized in a plant where it is necessary to eliminate the waste liquor formed during the desulfurization of 80,000 Nrn of coke oven gas per hour by the so called Perox process. The following materials are supplied or discharged through the various conduits illustrated in the drawing:

a) Through Conduit 1: 1.1 m /h waste liquor,

about C Containing: NH (free) about 17.0 g/] CO about 15.4 g/l (NHQ SO about 20.9 g/l (NHQ S Q, about 136.3 g/l N1-1 CNS about 190.8 g/l b) Through Conduit 9 and Conduit 9a: 0.78 m thickened waste liquor,

about 100 C Containing: NH; (free) about 14.4 g/l CO about 13.0 g/l (N1'1 SO about 29.5 g/l (NH S O about 192.4 g/l NH, CNS about 269.4 g/l c) Through Conduit 14: 617 Nm lh coke oven gas, 40 C Net calorific value (Hu) 4,500 kcal/nm d) Through Conduit 13: 968.6 kg/h NH vapors, 100 C e) Through Conduit 12: 3,664 Nm /h primary air, 40 C f) Through Conduits 12a and 12b: 23 l Nrn lh secondary air, 40 C g) Through Conduit 15: 4,822 Nm lh lean gas,

about 940 C 1,457 kg/h steam, 940 C h) Through Conduit 24: 4,775 Nm /h lean gas, about 160 C, Net calorific value (Hu) about 500 kcal/Nm N about 73.1% by vol.

-c ontinued Steam 1,778 kg/h about 160 C i) Through Conduit 20: about 85 kg/h sulfur k) Through Conduit 23: 2.8 metric tons/h saturated steam 3.5 atm. gage 1) Through Conduit 19: 3.1 metric tons/h boiler feed water. 104 C in) Through Conduit 25: 0.3 metric tons/h slurry.

With the herein described process, it is possible to eliminate the enriched waste liquor accumulated in the so called Perox system without discharging the waste liquor into the sewer. This solves the problems that were present in the operation of these plants before the herein described invention.

Further, the process of the invention is distinguished by the fact that the ammonia vapors NH accumulated in the treatment of the coke oven gas can be simultaneously eliminated so that the construction of an additional system for the combustion of ammonia is unnecessary. This results in only a very slight increase in the investment costs for the total plant for the treatment of coke oven gas by using the process of this invention since the additional costs resulting from the equipment for elimination of the waste liquor can be practically completely compensated by omitting the ammonia combustion. Since the ammonia vapors are not burned during the process of the present invention but are decomposed as lean gas and again added to the coke oven gas, no nitrogen oxides appear and lead to an undesired pollution of the atmosphere, as is present in the combustion of ammonia.

The amount of gas to be treated is increased by about 6% because of the addition of the lean gas accumulated in the process of the invention to the coke oven gas. The resultant costs, however, are minimal.

According to the provisions of the patent statutes, we have explained the principle, preferred construction and mode of operation of our invention and have illustrated and described what we now consider to represent its best embodiments. However, it should be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier comprising,

evaporating between about 30 and of water from the waste liquor to form a concentrated waste liquor,

introducing said concentrated waste liquor into a combustion chamber,

introducing air into said combustion chamber,

introducing a sufficient amount of coke oven gas to provide a reducing atmosphere in said combustion chamber,

thermally decomposing said concentrated waste liquor in said combustion chamber and forming a lean gas and sulfur,

separating the sulfur from the lean gas,

admixing the lean gas with coke oven gas evolved during a coking process.

2. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier as set forth in claim 1 which includes,

introducing amonia vapors evolved in the treatment of coke oven gas with an excess of oxygen into said combustion chamber.

3. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier as set forth in claim 2 which includes,

evolving amonia vapors while evaporating the water from said waste liquor,

admixing said amonia vapors with coke oven gas evolved during a coking process. 4. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with oration of water from said waste liquor. 

1. A PROCESS FOR THE ELIMINATION OF WASTE LIQUORS ACCUMULATED IN THE DESULFURIZATION OF COKE OVEN GAS WITH A WASHING SOLUTION CONTAINING AN ORGANIC OXYGEN CARRIER COMPRISING, EVAPORATING BETWEEN ABOUT 30 AND 70% OF WATER FROM THE WASTE LIQUOR TO FORM A CONCENTRATED WASTE LIQUOR, INTRODUCING SAID CONCENTRATED WASTE LIQUOR INTO A COMBUSTION CHAMBER, INTRODUCING AIR INTO SAID COMBUSTION CHAMBER, INTRODUCING A SUFFICIENT AMOUNT OF COKE OVEN GAS TO PROVIDE A REDUCING ATMOSPHERE IN SAID COMBUSTION CHAMBER, THERMALLY DECOMPOSING SAID CONCENTRATED WASTE LIQUOR IN SAID COMBUSTION CHAMBER AND FORMING A LEAN GAS AND SULFUR, SEPARATING THE SULFUR FROM THE LEAN GAS, ADMIXING THE LEAN GAS WITH COKE OVEN GAS EVOLVED DURING A COKING PROCESS.
 2. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier as set forth in claim 1 which includes, introducing amonia vapors evolved in the treatment of coke oven gas with an excess of oxygen into said combustion chamber.
 3. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier as set forth in claim 2 which includes, evolving amonia vapors while evaporating the water from said waste liquor, admixing said amonia vapors with coke oven gas evolved during a coking process.
 4. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier as set forth in claim 1 in which, said air introduced into said combustion chamber includes air utilized in the oxidation of said waste liquor.
 5. A process for the elimination of waste liquors accumulated in the desulfurization of coke oven gas with a washing solution containing an organic oxygen carrier as set forth in claim 1 which includes, cooling said lean gas in a waste heat boiler to provide steam for heating the waste liquor during the evaporation of wAter from said waste liquor. 